Got the kit in the end and tested water from the boiler. Still confused about what’s what after reading this thread again so I’m just being thick !!
Steam boiler 7 weeks after full drain and weekly cup draws.
20 ml samples 21.3 Celsius. only have 5 ml tubes so used cups and mixed using a spoon after every drop (hopefully this doesn’t alter the score)
TDS reader - 33
GH - 10 drops = 179 / 4 = 44.75
KH - 7 drops = 125.3 / 4 = 31.32
Photos of the final colours
Water from osmio zero with remineralisation cartridge
20ml samples 22.5 Celsius
TDS reader 34
GH - 6 drops = 107.4 / 4 = 26.85
KH - 5 drops (light yellow)/ 6 drops (brighter yellow) = 89.5 / 4 = 22.37 (light) / 107.4 / 4 = 26.85 (brighter)